An alternator generates a power for a vehicle and interworking with a pulley of an internal combustion engine through a V-belt.
The alternator is connected to a crank shaft of the engine by the V-belt. The alternator rotates at a speed faster by about two to three times than that of revolutions per minute (RPM) of the engine due to a diameter ratio between the pulley of the crank shaft and a pulley damper of the alternator.
In an accessory belt system, such as the alternator, the pulley of the crank shaft, and a water pump have a resonance frequency, causing system vibration, degrading durability of a belt, and increasing belt tension to degrade fuel efficiency.
Thus, recently, an overrunning alternator decoupler (OAD) damper pulley isolating system vibration by inserting a spring in a shaft of the alternator within a pulley body is commonly used.
As illustrated in FIG. 1, the OAD damper pulley according to the related art includes a pulley body 10 having belt recesses 11 formed on an outer circumferential surface thereof to receive power from a pulley of an engine through a belt. A shaft connection portion 20 is provided within the pulley body 10 and allows a rotational shaft of an alternator to be insertedly coupled therein. A torsion spring 30 is installed on an outer circumferential surface of the shaft connection portion 20 to reduce a variation of driving force transmitted from the pulley body 10. A clutch 40 is interposed between the torsion spring 30 and the pulley body 10 and blocks power transmission between the shaft connection portion 20 and the pulley body 10 when the power transmitted from the engine is instantly reduced.
Accordingly, rotational power from the engine is transmitted to the pulley body 10 through the belt and subsequently passes through the clutch 40, the torsion spring 30, and the shaft connection portion 20, so as to be transmitted to the alternator.
Here, however, in the OAD damper pulley structure according to the related art, a change in engine torque transmitted from the pulley body 10 to the shaft connection portion 20 is absorbed by only elastic force of the torsion spring 30 to reduce it, having a limitation in reducing damping by only the torsion spring 30.
Further, in the OAD damper pulley structure according to the related art, if the change in the engine torque is not sufficiently absorbed to be reduced, vibrations and noise may be generated to result in degradation of NVH performance of a vehicle, and thus, an appropriate solution thereto is required.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.